摘要:

A welded tubular T-joint is analysed using finite element methods to obtain through-thickness and surface stresses due to axial and in-plane bending loads. The effects of a shallow weld toe crack on the stress redistribution are studied. The two-dimensional analysis of the joint includes the membrane stiffness representation by plane stress element and the flexural stiffness by plate bending element. For the three-dimensional analyses, the joint is modelled using incompatible solid elements to improve flexural characteristics. The embedded elliptical crack front is modelled by straight-line segments. The region at the vicinity of the crack is discretized using special elements, which produce a singular stress field at the crack front.Key words: tubular joint, stress analysis, weld toe crack, incompatible element, singular element.

ISSN:0315-1468    

DOI:10.1139/l86-038

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Ten mode shapes, natural frequencies, and modal damping values have been measured for a steel-joist concrete-slab floor spanning 32.1 m. From ambient vibrations and steady-state shaker tests the frequency of the fundamental mode was determined to be 3.5 Hz, and the modal damping ratio to be approximately 1% of critical. A comparison of vibration criteria in Appendix G of CAN3-S16.1-M84 confirms satisfactory performance for walking, but for other rhythmic exercises disturbing vibrations developed. These occurred primarily at the forcing frequency of the exercises and not at floor resonance frequencies. Values of dynamic load factors, α, for rhythmic loadings of this floor were evaluated in accordance with the guidelines on floor vibrations in the Commentary to the National Building Code of Canada 1985.Key words: floors, gymnasiums, vibration tests, resonant frequencies, mode shapes, dynamic loads, dynamic response.

ISSN:0315-1468    

DOI:10.1139/l86-039

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

For small-span to medium-span bridges, the beam-and-slab type of construction is popular, mainly because of its ease of construction, and is preferred in practice even though this form of construction may sometimes exhibit rather poor transverse load distribution qualities. This deficiency is often reduced by the incorporation of one or more diaphragms in the deck construction. Although the use of diaphragms in beam-and-slab bridges is very extensive, their use is almost entirely empirical rather than based upon any logical method of analysis. Thus, the requirements for diaphragms that are found in codes of practice all over the world usually consist of simple and arbitrary statements. It is proposed here to carry out a thorough theoretical study of the structural behaviour of diaphragms in beam-and-slab bridges, with a view to establishing this behaviour on a well-reasoned footing.Key words: beam-and-slab bridge, diaphragm, cross frame, grillage analogy, finite element method, orthotropic plate theory.

ISSN:0315-1468    

DOI:10.1139/l86-040

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The advent of stormwater modelling techniques has resulted in the need for a Canadian urban design storm. As a first stage in meeting this need, a 1-h urban design storm has been developed. This design storm, which is fully described by two parameters and the rainfall depth as given by Atmospheric Environment Service (AES) intensity–duration–frequency data, is specified for a wide range of return periods for all regions of Canada. Extensive comparisons with observed 1-h storms, both in the temporal domain and the frequency domain, indicate that the two-parameter mathematical model is capable of simulating individual rainfall events and an average or 'design' event for any particular site. The design storm model has been extended on a regional basis by evaluating the two parameters for each of 45 AES stations across Canada. Regional values of the parameters have been derived so that a design storm can be determined for an area without rainfall records.Key words: design storm, urban drainage, storm water, rainfall, temporal distribution, regional analysis.

ISSN:0315-1468    

DOI:10.1139/l86-041

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

In 1982, N.K. Becker & Associates Ltd. designed a precast concrete flood protection and beach restoration system for the 3 km (2 mi) long Lake Erie shoreline of the City of Luna Pier, Michigan. The construction of these works, which included beach sills, shorewalls, and a marina basin, was completed in 1984.The shorewall system is unique in that it was designed of interconnected, open-ended, earth-filled, thin-walled precast concrete cylinders, placed on-end and in-line to form a continuous wall. This seawall design was selected by the City of Luna Pier over alternative systems because it was estimated to cost 50% less than conventional steel sheet piling or cast-in-place concrete systems.During the final design, hydraulic model tests were carried out at both the University of Michigan and the University of Windsor to study the uprush, scour, longshore transport, and wave pressure characteristics of the proposed system. The methods used to design this economical and functional flood protection system are presented along with an analysis of its performance to date.Key words: beach, beach sill, flushing, hydraulic model testing, ice, longshore drift, overtopping, precast cellular concrete wall system, scour, shorewall, uprush, water levels, waves, wave deflector.

ISSN:0315-1468    

DOI:10.1139/l86-042

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The presence of a cove, either natural or artificial, along a main watercourse is often considered to be an ideal location for a small harbor. However, when the current in the main channel is relatively large, an eddy is generated inside the small bay, thus hindering its use as a harbor for ships. The use of mathematical modelling of this phenomenon to find a solution to the problem is rather difficult. Based on a case study, i.e. a small artificial bay along the Saguenay River at Chicoutimi, Québec, a methodology is presented and a model developed to give a good representation of this phenomenon.Key words: flow, finite elements, harbor, modelling, vortex.

ISSN:0315-1468    

DOI:10.1139/l86-043

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A finite element analysis to predict the instability of soil–steel structures is presented. For the steel segment, beam–column elements that accommodate geometric nonlinearity as well as plastic hinge formation are used. Constant and linear strain triangular and quadrilateral elements simulate the soil media in conjunction with spring-type interface elements. A hyperbolic stress–strain relationship models the soil remote from the conduit; an elastoplastic soil model is chosen for regions of high stress gradients above and around the conduit. The formulation is capable of following the initiation and propagation of failure in the soil and its effect on the conduit stability. Analytical failure loads are compared with experimental results and those predicted by the Ontario Highway Bridge Design Code (OHBDC) and the American Association of State Highway and Transportation Officials (AASHTO) specifications.

ISSN:0315-1468    

DOI:10.1139/l86-044

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

For many concrete slabs without beams, the critical design factor is the shear stress in the vicinity of the column–slab junction. This is particularly so near edge and corner columns where the shear stresses due to the unbalanced moments may account for the major portion of these stresses. The determination of these design stresses in accordance with the provisions of Standard CAN3-A23.3-M84 is both time consuming and subject to numerical mistakes. Based on these provisions, design charts were developed, which greatly reduce the amount of calculation required and are suitable for routine use in the design of slabs. The use of the charts is illustrated by examples.Key words: design, flat plate, moment transfer, reinforced concrete, shear, slabs.

ISSN:0315-1468    

DOI:10.1139/l86-045

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The paper describes a relatively easy to use computer program for the analysis of steady state surface and energy profiles in networks of open channels. RIVER4 is intended primarily for use in a time-sharing environment to facilitate the trial and error setup and calibration and modification of networks of arbitrary geometry and connectivity. The networks may consist of natural and man-made open channels or sewer systems or both, in configurations of single reach, multiple tributaries, and bifurcated branches with resultant "island" flow. As well as regular reaches, the system description may include transition devices such as bridges, weirs, culverts, manholes, and diversion structures. The flow resistance equation is selected at run time, from six commonly used laws. System geometry is stored on secondary devices such as tapes or discs so that relatively large systems may be analysed in machines of modest size.Key words: backwater, channel, computer, design, flood, islands, networks, profiles, sewers.

ISSN:0315-1468    

DOI:10.1139/l86-046

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

This paper examines the role of short-chain volatile fatty acids in the excess biological phosphorus removal mechanism of the activated sludge process. The effectiveness of various substrate additions in inducing phosphorus removal was investigated through a series of laboratory and pilot-scale experiments. Phosphorus release and substrate uptake both take place in the anaerobic zone of the process and there appears to be an exchange phenomenon that occurs between the two molecules. The system phosphorus removal of the process is improved by the addition of sodium acetate to the anaerobic zone. It is important that the zone receives no incoming nitrate, as the added substrate will be oxidized in the denitrification reaction, rendering it unavailable for the phosphorus removal mechanism. Acetate and propionate, the two substrates that are most effective in inducing anaerobic phosphorus release, can be generated on-site at a treatment plant by primary sludge fermentation in concentrations sufficient to significantly enhance the phosphorus removal characteristics of the process.Key words: biological phosphorus removal, short-chain volatile fatty acids, phosphorus release, substrate utilization, primary sludge fermentation.

ISSN:0315-1468    

DOI:10.1139/l86-047

出版商:NRC Research Press    

年代:1986

数据来源: NRC